DE 103 10 448 A1 discloses an electromagnetic actuator comprising two coils and an armature. By applying a current to the coils, the armature is displaced in the axial direction.
DE 199 10 497 A1 describes a method, according to which the position of an armature in an actuator is detected with a coil by determining the differential induction of the coil. For this purpose, the current decrease time during a drop in current is determined as a time difference between two threshold values. The current drop time is highly dependent on the resistance of the coil, which is temperature-dependent.
Furthermore, DE 100 33 923 A1 discloses a method, according to which the position of an armature is determined as a function of the counter-induction created by the movement of an armature in a coil. The counter-induction is dependent on the velocity of the armature. If such an actuator is used in a fluid-filled space, the velocity of the armature is highly dependent on the viscosity of the fluid. Also the viscosity of the fluid is dependent on the temperature.
It is therefore the object of the invention to enable determination of the position of an actuating member in an electromagnetic actuator without additional sensors, wherein the position determination in particular is supposed to be independent of the temperature.